The present invention relates to a passive infrared intrusion detector. This type of detector includes a heat sensor, a lens for focusing heat energy on the heat sensor, and means operatively associated with the heat sensor for providing a detection signal when the heat sensor detects a sudden change of temperature, as for example, caused by the body heat of a passing intruder. One common example of a type of passive infrared intrusion detector incorporates a pyroelectric detector as the heat sensor.
One problem with known passive infrared intrusion detectors is that it is difficult to establish specific zones to be observed and protected by the detector before the detector is put into operation. It is imperative that the zones to be protected be directed away from any potential source of false alarms. Any surface or object which can change temperature rather rapidly is a source of false alarms. These sources include grills on heater ducts, light bulbs, air conditioners, and the like.
In the past, trial and error techniques have been used to focus infrared intrusion detectors away from sources of false alarms. For example, a source of heat (as for example a human body) was moved about in the zone desired to be protected while the intrusion detector was adjusted. The generation of an alarm signal indicated that the intrusion detector was focused on the desired zone to be protected. Such trial and error techniques were obviously time consuming and cumbersome.
It is an object of the present invention to provide a method and apparatus which utilizes a lamp which emits visible light to locate and establish zones to be protected by the detector before the intrusion detector is put into operation.